Photoreceptors of higher vertebrates, including primates, are to be explored microspectrophotometrically in optical isolation. The spectral characterization of in situ visual pigments will be carried out in the visible and near ultraviolet spectrum. Single cell optical density (OD), linear dichroism (LD), and bleaching difference (BD) spectra are to be measured. The specific aims are (1) to obtain accurate cone spectra from primates, (2) to find a method of preserving primate cone structure and pigment in suspension, (3) to develop a method to generate analog pigments in isolated photoreceptors, (4) to study wavelength regulation in visual pigments by the use of synthetic analogs of retinal in single cones, (5) to search for ultraviolet-absorbing visual pigments in dace, trout and goldfish, (6) to explore the role of water in rhodopsin films, (7) to study gecko photoreceptors, (8) to determine LD in anchovy cones, and (9) to continue the development of instrumentation for the measurement of circular dichroism in single cells. Long-term objectives are the understanding of chromophore-apoprotein interactions and their changes upon light absorption. These have importance in wavelength-tuning in pigment absorbances (spectroscopy) and in the signal production for visual excitation (photochemistry). The results of this work may be relevant to retinal degenerative diseases and to human color vision, normal and abnormal (color blindness).